The invention relates to measuring and testing torque using a rotating torque responsive element, but more particularly, the invention relates to apparatus for dynamically testing power transmission belts.
Four-square testing apparatus is used to determine the dynamic effect of horsepower and torque on power transmission components. In such apparatus, power is recirculated between two rotating shafts. The advantage of such drives is that input power is quite small compared to the power absorbed in the recirculating system. The input power need make up only for power losses of the system.
Preload torque in known quantity is easily introduced in apparatus where the shafts are mechanically interlocked with positive rotational devices such as gears. Starting with parallel shafts mechanically interconnected with spur gears, one shaft may be rotationally displaced from the other to preload a known torque in the two shafts. Rotation of either shaft by external means causes the preload torque to be dynamically recirculated between the two rotating shafts. While such apparatus is satisfactory for testing power transmission components where the shafts are mechanically interlocked, the apparatus is unsatisfactory for testing power transmission components where mechanical interlocking of the two shafts cannot be obtained. The apparatus is unsatisfactory for testing components which transmit power by means of friction. This is because the statically introduced torque is easily lost at the friction surfaces, leaving no preload for power recirculation.
In a type of four-square apparatus, it is known to have two parallel shafts with two pulleys of different diameters mounted on each shaft. The pulleys are arranged so the large pulley of one shaft is aligned with the smaller pulley of the other shaft. The difference in pulley diameters is chosen for a predetermined speed ratio. Two V-belts are arranged over the pulleys and preloaded. One shaft is rotated. The difference in speed ratio causes power to recirculate between the belts. A problem associated with such a device is that of determining the tension in each belt. This is because belts typically stretch and wear down in width during their normal service life and they are built with circumferential tolerances. While the torque between two belts could be measured, their contribution and their share of a recirculating horsepower load is indeterminate because of the unknown tensions. Also, the torque arising from a given ratio cannot be predicted ahead of time because of variations in belt transverse and longitudinal elastic characteristics.
Representative of the art is U.S. Pat. No. 3,956,929 (1976) to Jenkins et al. which discloses a testing apparatus including a fixed shaft and a floating shaft with means for moving it selectively generally parallel to the fixed shaft, two pulleys on each shaft paired and aligned between shafts and wherein one of the pulleys is the selectively variable diameter type.
What is needed is a belt test apparatus having a magnetic particle clutch selectively engagable such that a differential belt speed provides for energy recovery during testing of at least two belts. The present invention meets this need.